4R8's table build

[Mayhem]

(11-14-2012, 10:51 AM)4R8 Wrote: ...what's the plural of axis?...

Axes

[4R8]

(11-14-2012, 11:01 AM)Mayhem Wrote:

(11-14-2012, 10:51 AM)4R8 Wrote: ...what's the plural of axis?...

Axes

ah, I knew it's be something simple! Thanks

back to some details. I was asked about 'V rails', the method I'm using for the motion of the machine. I'll follow that with a bit on the carriages so far.

V rails 101.

thee profile of a V rail is seen below



A V bearing is used to run along it



Generally you want to build a bit of adjustment into the machine to take up any play in the resulting mechanism. The most effective way I've encountered and used is via an eccentric bush.
In the photo above and below, the hex piece has been turned down on the lathe and an eccentric bore drilled through. By backing off the button head bolt and turning the bush, the bearings can be forced into the V rail, taking up any play in the motion.



another point to note with V rails and one of the best features for plasma and routing applications is their self cleaning design.
Any dust that settles on the rail is literally 'swept' off by the bearing as it passes. The angled surfaces also mean larger pieces simply fall off, not settling and causing an issue.

Standard roller bearings have no sweeping motion on the flat surface they run on. This means and debris on the surface is not removed, instead it can be embedded into the surface and can build up over time. Larger pieces may cause a jam/stall and ruin a part.

The ability to easily join sections together and change any singular bearing should one fail makes the V rail system extremely attractive to many builders and myself.

There are many other options to consider and all have their pros and cons.

skate bearings on flat bar, round bar or angle, linear bearing systems and slides. Namely the round hardened rails and Hiwin style slides can all be used but I've chosen V rails

[stevec]

Hey Greg, you could cut your rack on the underside of the V rails?

[4R8]

The carriages

The Y axis cariage (Zcarrier) is below. it uses three 12mm V groove bearings which have an OD of a little over 45mm.
All three are mounted on eccentric bushes to allow adjustment
The material used in construction is 10mm aluminium. For these sorts of projects I like to tape the stock off with masking tape to draw on the design to be milled, drilled and tapped. That way any changes are easy to make and by removing the tape from places where material will be removed gives a better indication on what the final piece will look like.



This one shows an X axis support. It also shows a failed layout. As there is two of these identical parts, the measurements were referenced from this layout and re-marked on the opposing side. the two parts then placed on the mill and drilled/milled as one using the other plates' markings.
The rails are smaller on this axis to keep the cost down a little. it uses 3/8" V bearings which have an OD of a little over 30mm (just to mix up metric/inch measurements)

[4R8]

(11-15-2012, 11:46 AM)stevec Wrote: Hey Greg, you could cut your rack on the underside of the V rails?

The only problem is that the flange is only 6mm thick on the Yaxis and 4mm on the X



The other pics do make it look alot larger then reality.

[f350ca]

Thought about that Steve. Ended up getting 1/4 thick flat bar for the Y axis to bolt on and 1/4 x 1 angle for the X. Then 3/8 to make the racks. Went angle for the X incase the main frame isn't straight. If I oversize the holes I can pull the track straight and aligned to each other. Up and down isn't critical, and the torch height control should take care of it.
4R8, (we need a name) Great info!!!!
Do the 3 bearings on the two tracks have any slack in the x direction? That is what I was thinking of doing, great for someone else to test it.
What did you do to the inside of the Y axis square tube to bolt the side plates on?
Your v rails are exactly what I'm hoping to mill out of cold roll flat bar,, won't be hardened but at my age I don't buy green bananas so doubt if I'd ever wear them out.
Are there 2 races in the wheels? My plan was to turn the wheel and press two skate board bearings in.
I used eccentrics similar to yours for the vertical movement on the sawmill carriage, but used flat topped rails, your right they build up, even vertically.
Do the wheels float sideways on one end of the Y axis? On things like crane tracks and the sawmill I find it beter to steer from one side and let the other float a bit to avoid binding. The two motors should keep it straight anyway.
Hope we're not throughing too many questions at you, all great and timely info for me.
Thanks.

[4R8]

I'll throw my name in my sig line, just haven;t got around to doing it yet. Jason.

The rigidity really is very good. The eccentric bushes allow a very snug fit to the rail. I've got a few tight spots to sport but i suspect these will be sorted once the burs on the back side of the rails and the Al flatbar they're mounted to is cleaned up.

The end plates are bolted onto the end of the gantry tube. I've welded a piece of 6mm plate in the ends (set in approx 6mm incase for some reason the ends needed further dressing or squaring) which has been tapped to accept the stainless countersunk M12 bolts.

Yes, there's two races in the bearings. See for details---> http://www.vxb.com/Merchant2/merchant.mv...e-Bearings
Just don't look at the price of the buggers!

I've got both sides running without float. There's enough adjustment in the frame to allow both to run true along the rails.
I may down the track, when space permits, increase the machine size. In that case, I'd float one side. I can't see an issue squaring a 5x5 table.

Questions are fine, that's what these places are for. I wish i asked more earlier on!

[stevec]

Jason, do you have some sort of unending supply of nifty button head bolts? I'm sorta a minimalist when it comes to work or expense and being a no "green banana" buyer like Greg.
Just curious to see if you really need to bolt so frequently. I'm not being critical, just trying to educate myself (even at my age).

[4R8]

(11-15-2012, 05:54 PM)stevec Wrote: Jason, do you have some sort of unending supply of nifty button head bolts? I'm sorta a minimalist when it comes to work or expense and being a no "green banana" buyer like Greg.

I sort of have an unofficial supply of stainless fasteners......
http://stainlessstore.com.au/
These are the guys I use, their prices are simply incredible, even when they used to charge shipping, it was cheaper then going to hardware store and getting "trade discount"

whenever I size is required that I don't have on hand, I'll buy a box.
I'm a "green banana type" and love to have things on hand if needed. The only problem is finding s spot to keep everything! I'm thinking of building two workshops in the local industrial area, renting one out and using the other for myself. Just need to justify it to my partner. Hopefully once the machine is complete, I have good reason to!

(11-15-2012, 05:54 PM)stevec Wrote: Just curious to see if you really need to bolt so frequently. I'm not being critical, just trying to educate myself (even at my age).

The rails are bolted every 100mm, is it too many? Quite possibly. I really can't give an answer with any calculations. I just saw the mounting flange thickness of ~4mm on X and thought I'd play safe, especially considering I want to try light routing on the machine later down the track.
I also wanted to have the spacing less than that of the V bearings on the carriages and gantry side plates.

I'll post up control console details tonight!

[f350ca]

Jason,
Did you use aluminum tube for the gantry? I picked up 5 feet of 3x3 inch .120 wall for mine. Haven't miked it yet, hoping it will be accurate enough to position the tracks.